<?php

/**
 * PHPExcel
 *
 * Copyright (c) 2006 - 2013 PHPExcel
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * @category   PHPExcel
 * @package	PHPExcel_Shared
 * @copyright  Copyright (c) 2006 - 2013 PHPExcel (http://www.codeplex.com/PHPExcel)
 * @license	http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt	LGPL
 * @version	1.7.9, 2013-06-02
 */

/**
 * PHPExcel_Shared_TimeZone
 *
 * @category   PHPExcel
 * @package	PHPExcel_Shared
 * @copyright  Copyright (c) 2006 - 2013 PHPExcel (http://www.codeplex.com/PHPExcel)
 */
class PHPExcel_Shared_TimeZone
{
    /*
     * Default Timezone used for date/time conversions
     *
     * @private
     * @var	string
     */

    protected static $_timezone = 'UTC';

    /**
     * Validate a Timezone name
     *
     * @param	 string		$timezone			Time zone (e.g. 'Europe/London')
     * @return	 boolean						Success or failure
     */
    public static function _validateTimeZone($timezone)
    {
        if (in_array($timezone, DateTimeZone::listIdentifiers()))
        {
            return TRUE;
        }
        return FALSE;
    }

    /**
     * Set the Default Timezone used for date/time conversions
     *
     * @param	 string		$timezone			Time zone (e.g. 'Europe/London')
     * @return	 boolean						Success or failure
     */
    public static function setTimeZone($timezone)
    {
        if (self::_validateTimezone($timezone))
        {
            self::$_timezone = $timezone;
            return TRUE;
        }
        return FALSE;
    }

//	function setTimezone()

    /**
     * Return the Default Timezone used for date/time conversions
     *
     * @return	 string		Timezone (e.g. 'Europe/London')
     */
    public static function getTimeZone()
    {
        return self::$_timezone;
    }

//	function getTimezone()

    /**
     * 	Return the Timezone transition for the specified timezone and timestamp
     *
     * 	@param		DateTimeZone	 	$objTimezone	The timezone for finding the transitions
     * 	@param		integer	 			$timestamp		PHP date/time value for finding the current transition
     * 	@return	 	array				The current transition details
     */
    private static function _getTimezoneTransitions($objTimezone, $timestamp)
    {
        $allTransitions = $objTimezone->getTransitions();
        $transitions    = array();
        foreach ($allTransitions as $key => $transition)
        {
            if ($transition['ts'] > $timestamp)
            {
                $transitions[] = ($key > 0) ? $allTransitions[$key - 1] : $transition;
                break;
            }
            if (empty($transitions))
            {
                $transitions[] = end($allTransitions);
            }
        }

        return $transitions;
    }

    /**
     * 	Return the Timezone offset used for date/time conversions to/from UST
     * 	This requires both the timezone and the calculated date/time to allow for local DST
     *
     * 	@param		string	 			$timezone		The timezone for finding the adjustment to UST
     * 	@param		integer	 			$timestamp		PHP date/time value
     * 	@return	 	integer				Number of seconds for timezone adjustment
     * 	@throws		PHPExcel_Exception
     */
    public static function getTimeZoneAdjustment($timezone, $timestamp)
    {
        if ($timezone !== NULL)
        {
            if (!self::_validateTimezone($timezone))
            {
                throw new PHPExcel_Exception("Invalid timezone " . $timezone);
            }
        }
        else
        {
            $timezone = self::$_timezone;
        }

        if ($timezone == 'UST')
        {
            return 0;
        }

        $objTimezone = new DateTimeZone($timezone);
        if (version_compare(PHP_VERSION, '5.3.0') >= 0)
        {
            $transitions = $objTimezone->getTransitions($timestamp, $timestamp);
        }
        else
        {
            $transitions = self::_getTimezoneTransitions($objTimezone, $timestamp);
        }

        return (count($transitions) > 0) ? $transitions[0]['offset'] : 0;
    }

}
